Multi-spectral imaging with almost-full fill-factor using 3D pixels

Abstract

Image systems having three dimensional pixels. Each pixel is comprised of a substrate and a three dimensional stack of color sensors. Wavelength sensitive color reflectors are inserted between the individual color sensors and the semiconductor substrate. Incoming photons are partially converted into an electric charge in a color sensor. The unabsorbed portion is wavelength-selectively reflected to produce additional charge in the color sensor. The transmitted portion passes into a lower color sensor to produce an electric charge in that lower color sensor. The unabsorbed portion is wavelength-selectively reflected by another color reflector to produce additional charge in the lower color sensor. The process repeats for still lower color sensors/color reflectors. The substrate includes logic to interrogate the color sensors. Electrical conductors connect the substrate to the individual color sensors.

1 . An imaging sensor comprising a plurality of pixels, where each of said pixels comprises a semiconductor substrate and a three-dimensional stack of color sensors on the semiconductor substrate.  
   
   
       2 . The imaging sensor of  claim 1 , further including a plurality of color reflectors, wherein each pair of color sensors is separated by one of said color reflectors, and wherein the semiconductor substrate and the three-dimensional stack of color sensors is separated by one of said color reflectors.  
   
   
       3 . The imaging sensor of  claim 2 , wherein each color reflector reflects a different color spectrum.  
   
   
       4 . The imaging sensor of  claim 3 , wherein each color reflector is a Bragg reflector.  
   
   
       5 . The imaging sensor of  claim 1 , further including connectors that electrically connect each color sensor to logic on the semiconductor substrate.  
   
   
       6 . The imaging sensor of  claim 1 , wherein each color sensor includes a photo-sensor and a plurality of transistors for interrogating photo-induced charges generated by said photo-sensor.  
   
   
       7 . The imaging sensor of  claim 6 , wherein each color sensor is a CMOS active sensor.  
   
   
       8 . The color imaging devices of  claim 6 , wherein said semiconductor substrate includes row decoder and a column decoder.  
   
   
       9 . The color imaging devices of  claim 3 , wherein the color reflector that reflects the longest set of wavelengths is between the semiconductor substrate and the three-dimensional stack of color sensors, and wherein the color reflector that reflects the shortest set of wavelengths is furthest from said semiconductor substrate.  
   
   
       10 . The color imaging devices of  claim 9 , wherein each color sensor has a different thickness, wherein the thickest color sensor is adjacent to said color reflector that reflects the longest set of wavelengths, and wherein the thinnest color sensor is furthest from said semiconductor substrate.  
   
   
       11 . An imaging sensor comprising: 
 a semiconductor substrate having a plurality of crossing row and column conductors;    a row decoder for selectively applying potentials to a set of row conductors;    a column decoder for selectively reading charges on a set of column conductors;    a pixel matrix comprised of a plurality of pixels, where each of said pixels is located adjacent to one of said crossings of row and column conductors, wherein each pixel includes a three-dimensional stack of color sensors on said semiconductor substrate; and    electrical connectors that electrically connect each color sensor to one of said row conductors and to one of said column conductors.    
   
   
       12 . The imaging sensor of  claim 11 , wherein each pixel includes a plurality of color reflectors, wherein each pair of color sensors is separated by one of said color reflectors, and wherein the semiconductor substrate and the three-dimensional stack of color sensors is separated by one of said color reflectors.  
   
   
       13 . The imaging sensor of  claim 12 , wherein each color reflector reflects a predetermined color spectrum.  
   
   
       14 . The imaging sensor of  claim 13 , wherein each color reflector reflects a different color spectrum, wherein one of said color reflectors that reflects a longest set of wavelengths is between the semiconductor substrate and the three-dimensional stack of color sensors, and wherein one of said color reflectors that reflects a shortest set of wavelengths is furthest from said semiconductor substrate.  
   
   
       15 . The imaging sensor of  claim 14 , wherein each color sensor has a photo-sensor, wherein the color sensor adjacent said color reflector that reflects the longest set of wavelengths has a photo-sensor that is thicker than the photo-sensor of the color sensor furthest from said semiconductor substrate.  
   
   
       16 . The imaging sensor of  claim 13 , wherein each color reflector is Bragg reflector.  
   
   
       17 . The imaging sensor of  claim 11 , wherein each color sensor includes a photo-sensor and a plurality of transistors for interrogating photo-induced charges generated by said photo-sensor.  
   
   
       18 . A method of imaging, comprising the steps of: 
 converting a first portion of incoming light into a first electric charge;    reflecting a second portion of the incoming light and converting said second portion into additional first electric charge;    passing the remaining incoming light through a material while reflecting the second portion;    converting a third portion of incoming light into a second electric charge;    reflecting a fourth portion of the incoming light and converting said fourth portion into additional second electric charge;    passing the remaining incoming light through a material while reflecting the fourth portion;    converting a fifth portion of incoming light into a third electric charge; and    reflecting a sixth portion of the incoming light and converting said sixth portion into additional third electric charge.    
   
   
       19 . The method of imaging according to  claim 18 , further including the steps of interrogating said first electric charge to determine the intensity of a first color spectrum, interrogating said second electric charge to determine the intensity of a second color spectrum, and interrogating said third electric charge to determine the intensity of a third color spectrum.  
   
   
       20 . The method of imaging according to  claim 18 , further including passing the remaining incoming light through a material while reflecting the sixth portion.